1. Field of Invention
This invention relates to toilet flush tanks, more specifically, it is a simple two-level valve that retrofits into existing tanks to reduce water usage.
2. Background and Description of Prior Art
Expanding cities, ecological concerns, and reoccurring droughts have increased the need for water conservation. Flush-tank toilets are a major water user, accounting for about 38% of indoor residential water use. In response to this the federal government has recently required all new toilets to use no more than 1.6 gallons per flush. This has been accomplished by redesigning the toilet bowl and siphon. But this has done nothing to help the millions of 3.5 and 5.5 gallon toilets now in use. The cost of replacing them with new toilets is too discouraging to most owners. The savings in water bills only pays for the cost of replacement where water rates are extremely high, and then it takes 20 to 30 years. A device is needed that retrofits into existing toilets to make them comparable in water usage to the new toilets.
Some past devices have reduced the depth of water in the tank. This has reduced the pressure head at the bottom of the tank which reduces the velocity of the water flowing into the toilet bowl. The velocity is needed to carry waste out of the bowl through the siphon. Consequently, these devices cannot reduce the depth of water in the tank very much, before the flush becomes ineffective.
Other devices such as U.S. Pat. No. 4,467,482 (Dyer, Aug. 28, 1984) and U.S. Pat. No. 5,153,948 (Smith et al., Oct. 13, 1992) use a full tank., but close the valve early to make a short-duration flush. When set at the optimum level, these devices can flush out liquid waste and toilet paper with just over 1.6 gallons of water. They can often flush out solid waste at that level too. But unless they are set to higher levels, they leave dirty water in the bowl and din on the sides of the bowl. This results in a water wasting second flush. Also, waste sometimes gets trapped in the bowl side of the siphon just out of sight. And once in a while, pesky, extra buoyant pieces of waste require all the water in the tank to flush them out. Another problem is that these devices do not allow the toilet bowl to refill completely. More water in the bowl helps in the next flush to start the water moving quicker.
Because of the above problems early-closing valves are not common place. A two-level system that uses a short duration flush for liquids and a longer flush for solids can be more successful. Numerous systems that do this have been patented. Unfortunately, very few of them have reached the stores and none have caught on and found success with the public. An examination of them shows why.
These two-level systems commonly use complex mechanisms such as large siphons in the tank, water spray pushing the valve shut, hydraulic pistons, electrical controls, barriers dividing the tank into compartments, or valves at different levels. They are much too complicated for such a simple function. They require new openings in the tank, supports some how fastened to the tank, special control knobs, and a trained technician to install them. Many are large and bulky. Some won't actually fit inside the tank. Packaging and shipping are expensive and they cannot be attractively displayed in the stores.
Other two-level systems claim to be simpler. They usually use a mechanism that knocks the valve shut early or a valve that opens only part way so that the current closes it. Although somewhat simpler they still need intricate methods to control when the valve closes. They still do not compete with the simplicity and economy of the common flapper valve. Most buyers are not ecologically minded enough to buy something where they do not clearly see a quick financial saving. Also, because these inventions use a number of moving parts, they have a greater chance of wearing out or malfunctioning than does the flapper valve. Buyers want something dependable that they can install and forget about.
Some two-level systems such as U.S. Pat. No. 2,636,184 (Skutt, et. al., Feb. 12, 1951) and U.S. Pat. No. 4,365,364 (Riedel, Dec. 28, 1982) are simple and economical but are completely manual. Users must judge how long to hold down the flush handle by counting seconds or observing the contents of the toilet bowl. This is hard for children to learn and users do not want to give up the easiness of the usual way of flushing a toilet.
U.S. Pat. No. 4,937,894 (Hill, et. al., Jul. 3, 1990), U.S. Pat. No. 4,160,294 (Crumby, Jul. 10, 1979), and U.S. Pat. No. 4,328,596 (Renz, May 11, 1982) have some similarities to the present invention. Serious oversights in their design have made each of them inoperative.
All of the above two-level inventions suffer the same problem as the one level ones that close the valve early. The bowl is refilled from the same ball cock that refills the tank. Since it takes less time to refill a half-empty tank there is not enough time to refill the bowl completely. This diminishes the effectiveness of the next flush and annoys users. Users think their toilet is not working well if the bowl does not fill up like it used to.